For the record, I don't have any FA weapons. In fact, I don't currently have any NFA devices whatsoever. I am planning on some SBR's soon, but am sticking to cranks and bumpfiring for my own guns.
That being said, I do have friends with FA guns that I get to shoot from time to time. Some of them have an 07/02 and have built a post-sample MG42, which ROCKS!
I have a lot of design ideas, most of which never even make it onto paper. I like my idea about a .22lr SA42-type gun more than an M16 upper better anyway. Mostly because I don't have an M16 lower and sometimes get to shoot the real thing.
Imagine a MG42 twin AA mount with a 8mm SA42 and a .22lr SA42-type. Why? Why not!
As I've mentioned too many times before, I like that kind of silliness: